Emergency brake light

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67F100JMA
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Emergency brake light

Post by 67F100JMA »

Finally made one good wire harness from the two that i had everything seems to be working good, the only thing I didn't find is where the emergency brake light connects to, I have no idea where to connected to, any help would be appreciated thankyou
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knightfire83
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Re: Emergency brake light

Post by knightfire83 »

The positive feed is from the ignition switch "run" position.

The ground for it runs to the switch on the brake differential valve.

The switch, located on the brake differential valve, has two connections. #1 as explained above, goes to the brake warning lamp. #2 goes to the ignition switch "prove out" terminal that grounds when starting. Inside the switch they are both connected together in parallel.

In operation, the switch itself only acts as a ground. With good brakes, there is no ground from the switch. The light is not on.

However to check that the bulb is working and that the circuit is operational (connector is connected at the switch,) the ignition switch sends a ground to the switch via the "prove out" terminal and the bulb illuminates.

It is really quite neat how they designed that circuit, unplug the connector at the switch, and the bulb wont illuminate or "prove" that the circuit is working when starting, because there is no way for the ignition switch ground to feed back up to the light and illuminate it.
1974 Ford F-100 4x4- 360 / manual.
1970 Ford F250 4x4 ~ Sold.
67F100JMA
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Re: Emergency brake light

Post by 67F100JMA »

Ok I get it now, thankyou knightfire83. :thup:
I'll try it this weekend
67F100JMA
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Re: Emergency brake light

Post by 67F100JMA »

:fr:
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